Sheet metal drums or pails of cylindrical configuration generally fall into two main categories, namely open head pails or drums, and closed head pails or drums. Closed head drums normally have a permanently fastened top or head incorporating a small threaded closure of approximately 50 mm diameter through which the liquid contents of the drum may be discharged. By way of comparison open head drums, variously called open head, full open head, full open top or removable top, have a large circular removable lid which is engaged with a rim around the upper periphery of the cylindrical part of the drum. While closed head drums are suitable for the carriage of low viscosity liquids which may be easily poured into, and pumped or poured from the small closure in the lid of the drum, it is preferred to use open head drums for the carriage of viscous liquids such as adhesives or paints, and also for the carriage of granular solids.
Sheet metal drums or pails are commonly required for use in the transport of dangerous goods for which the leak tightness of the container as a whole, and especially the closure region, must be tested for approval by design-type qualification testing. The leak tightness of dangerous goods containers must be capable of being preserved, even in situations where the closure is severly and permanently deformed by impact or internal pressure. Drop testing is commonly carried out by dropping a laden container from a prescribed height onto a hard surface in various different orientations such that the container must survive being dropped onto its side, its lid, or at an angle where the upper rim of the container first contacts the ground surface at a prescribed angle. Such forms of testing for dangerous goods containers have recently been made considerably more stringent in various jurisdictions and it has been suggested that conventional open head drums will no longer be permitted for the storage and/or carriage of many categories of dangerous goods for which they have been in wide use for some considerable time.
Many solids and liquids are categorized as dangerous goods. Many liquid paints and adhesives, for example, are so categorized because inflammable components are used in their formulation. It has therefore become a need felt by purchasers and users of open head type drums for an improvement in the construction of the closure region so that this type of drum or pail can continue to be approved by the appropriate authorities for the storage and/or transportation of those dangerous goods for which they have existing market acceptance.
It is also commercially desirable that such improvements to the closure region of an open head drum or pail be achieved with not more than a small incremental cost increase to the existing, market accepted, drums or other similar types of container.
It is therefore an object of the present invention to provide a cylindrical open head sheet metal pail or drum which will obviate or minimise the foregoing disadvantages or which will go at least part of the way toward meeting the foregoing desiderata in a simple yet effective manner, or which will at least provide the public with a useful choice.